This invention relates in general to power driven wrenches and deals more particularly with an improved power operated socket wrench assembly of the type which includes a removable socket wrench unit particularly adapted for driving and setting nuts situated in relatively inaccessible locations. Socket wrench assemblies of the aforedescribed type heretofore available have generally included a wrench unit held in assembly with an associated drive unit by a plurality of fasteners which must be removed to release the wrench unit from assembly with its drive unit. While such power tools are generally well suited for long run production, the time required to separate one wrench unit from its drive unit and substitute another wrench unit of a different size render such a tool unsuitable for general purpose use or short run production where frequent changes of wrench size may be required. The present invention is concerned with this problem.